Disease Management Highlights from 2018 Apple Research at Cornell AgriTech Kerik D. Cox NYSAES Plant Pathology and Plant-Microbe Biology Section School of Integrative Plant Science Cornell University
Disease Management Highlights
from 2018 Apple Research at
Cornell AgriTech
Kerik D. Cox
NYSAES
Plant Pathology and Plant-Microbe Biology Section
School of Integrative Plant Science
Cornell University
Outline
• Efficacy of new fungicides for apple
scab and powdery mildew
management
• Prohexadione Ca2+ for fire blight
management
– Blossom blight
– Shoot blight
Apple scab & powdery mildew
concerns in 2018
• Secondary apple scab
pressure light April to July
rains: 7 infections in 2018
vs 13 in 2017
• SDHI fungicides – remain
effective
• Dry warm weather kept
mildew pressure high in
2018 vs wet cold in 2017
Apple scab & powdery mildew trials
• 3.1-acre planting site Empire’ and ‘Jonagold’-
M.9/M.111 interstem (18-20 years old)
• Widely-spaced two tree plots
Apple scab & powdery mildew trials
• Fungicide treatments
– Dilute handgun application timed at 7-10 day intervals
from TC- 2nd cover or 14-21 days from 3rd-7th cover
– Alternated with effective protectant standards ➔ not to
exceed max applications (4 applications)
Apple scab trials
• Apple scab evaluation
– Incidence any lesion on cluster leaves and fruit
(June), terminal leaf scab (July), & fruit (Sept)
Cluster leaves & fruit (June) Terminal leaves (July) Mature fruit (Sept)
Apple scab trials (2016)
• Dry year – little fruit infection: SDHI(premixes) better than
protectants, Miravis, Luna tranquility, Aprovia ≥ DMIs
Apple scab trials (2017)
• Wet year – high levels of fruit infection: Aprovia, Miravis,
Luna tranquility, Sercadis, SDHI(premixes), > protectant & DMIs
Apple scab trials (2018)
• Dry year – low levels of fruit infection: Aprovia, Miravis,
Luna tranquility, Sercadis, SDHI(premixes) – work well
Apple scab trials:
Trends and considerations
• Apple Scab
– DMIs still work on DMI resistant populations in
dry years
– QoI/SDHI premixes may be affected by
practical resistant to QoI fungicides in wet years
– Stand alone SDHI fungicides strong against
apple scab: Aprovia & Miravis highly potent
Powdery mildew trials
Disease assessment
• Powdery mildew:
– Primary mildew (June) & Secondary mildew (July)
– Incidence (any lesion) & Severity (% leaf area)
Powdery mildew trials (2016)
• Dry year high mildew pressure: SDHI premixes,
HS DMIs (Rhyme & Rally) > standalone SDHIs
Powdery mildew trials (2017)
• Wet year low mildew pressure : SDHI premixes,
HS DMIs (Rhyme & Rally), Miravis
Powdery mildew trials (2018)
• Dry year high mildew pressure : SDHI premixes,
HS DMIs (Rhyme), Miravis
Powdery mildew trials:
Trends and considerations
• Powdery mildew
– Resistance to DMIs in 2018: Topguard (Rhyme)
or Rally
– QoIs & SDHI-QoI premixes next best line of
defense – even with QoI resistance
– Stand alone SDHI fungicides slight effect against
mildew under high pressure, Miravis
– Sulfur 3.33 lbs/100 7-10 day intervals from bloom
to end of terminal growth = QoIs: phyto & smell
Outline
• Efficacy of new fungicides for apple scab
powdery mildew management
• Prohexadione Ca2+ for fire blight
management
– Blossom blight
– Shoot blight
Shoot Blight Management
• Prohexadione calcium (PhCa; Apogee): most
effective > works internally > slows
establishment of young trees
• Could prohexadione calcium help control
blossom blight and reduce shoot blight if
applied at pink?
• Could we use prohexadione calcium more
effectively with low rates and different
timings?
2016-18 PhCa Research
• 13 year old ‘Gala’ on B.9
rootstock
• Artificial inoculum for
blossom blight (Ea 273
at 1x106 CFUml-1) >
serve as inoculum for
shoot blight
• Inoculated @ 80%
bloom
2018 PhCa Research
• 2nd leaf ‘Gala’ on G.202
rootstock
• No inoculum: measure
effects on fruit set, shoot
growth, & TCA only
• Assessments in late
June & early Oct
2016-18 PhCa Research
Treatments
• Untreated: no control of fire blight, no impact on tree
productivity
• Antibiotics: Streptomycin and Kasugamycin; impact
on fire blight, no impact on tree productivity
• Natural SAR: Regalia; organic option, impact on fire
blight, no impact on tree productivity
• Apogee (prohexadione calcium – growth regulator)
pink applications, standard program, season-long
programs of low rate applications
2016-18 PhCa Research
Assessments
• Blossom and shoot
blight
• Crop load, fruit size,
TCA, & shoot length:
late June – early Oct
Could prohexadione calcium help
control blossom blight and reduce
shoot blight if applied at pink?
Research Question
2017Results: Blossom Blight
PhCa
2018
Low High
2016
Cell wall widths in cortical parenchyma of petiole cross sections
Treatments5/11
Full Bloom5/18
SamplingPre-treatment: 5/11Post 1: 5/22Post 2: 6/27
100μm
June 27 (~40 DAFB) Apogee @ 6oz/100gal
Cell Wall Thickness 40 DAFB
Results: Shoot Blight
2017
PhCaLow High
2018
2016
Pink applications > Shoot Length
2016 2017PhCa PhCa
Dry Year Wet Year
2018 2018: 2 year old ‘NY1’
PhCa PhCa
Pink applications > Shoot Length
Dry (June) then Wet (August) Year
Pink > Fire blight & Growth
• PhCa at Pink:
– 1) Decent BB & SB
control (best at 6 oz)
– 2) Reduce bitter pit too?
Pink application is
recommended for
cultivars prone to bitter
rot
– 3) Manage high vigor
varieties – holding tree
training
Pink > Fire blight & Growth
• PhCa at Pink:
– 4) Better with biological at bloom reduce inoculum;
– 5) No impact on shoot growth by end of season
(early on yes)
– 6) Thickened pedicel cell walls 40 DAFB – apply
earlier, Tight Cluster?
• Regalia (natural SAR):
– 1) Decent BB & SB control (best with copper)
– 2) No impact on shoot growth
Can we use prohexadione calcium
more effectively with low rates and
multiple timings after petal fall?
Research Question
PF+ programs on Shoot blight
Petal Fall programs: Double Nickel LC 32 fl oz @ Bloom
PF+ on shoot length in Sept2016 Dry Season 2017 Wet Season
Mean
sh
oo
t le
ng
th (
cm
)
Prolonged use programs of Apogee most impact on growth both years
PF+ programs on Shoot blight
Petal Fall programs: Double Nickel LC 32 fl oz @ Bloom
2018 Dry Early & Wet Late Season
PF+ on shoot length in Sept
Both std and low rate apogee similar in impact on growth in 2018
2018 Dry Early & Wet Late Season
PF + on Shoot blight & Growth
• Low rates of PhCa after petal fall:
– 1) Can effectively manage shoot blight > not
always be improved over std program
– 2) Start early with low rate programs
– 3) Prolonged programs of low doses > slightly
impede trees
• Regalia (natural SAR):
– 1) Good control of SB infections
– 2) No impact on shoot growth
2019 PhCa Research
Further refine prohexadione calcium applications
at “pink” & season-long prohexadione calcium
programs on young trees with no fire blight
2018: 2 year old ‘NY1’
PhCa
Acknowledgements
Lab Members,
Undergraduates,
& Technicians
Katrin Ayer
David Strickland
Stephanie Smart
Daniel Kaplan
Matthew Siemon
Mei Wah Choi
Funding Sources
Apple Research and Development Program
North American Agrichemical Industry:
Syngenta, BASF, Bayer, Dow, & Dupont, Marrone Bio
Innovations, Certis